Method of detecting the reciprocal position between a cylinder and a piston a hydraulic or pneumatic cylinder-piston unit, as well as cylinder-piston unit for implementing such method

Abstract

A method for detecting the reciprocal position between a cylinder and a piston in a cylinder-piston unit, including the following phases: setup of a cylinder-piston unit featuring at least one tubular body ( 2 ) presenting at least one passing accommodation host ( 6 ); at least one moving body ( 5 ) which can be longitudinally shifted in the tubular body ( 2 ), featuring at least one reference area ( 5 c ) extending for a portion ( 5 d ) on the surface of the moving body ( 5 ); a detector ( 7 ) which can be accommodated in such passing accommodation host ( 6 ), oriented towards the moving body ( 5 ) and detecting the presence or absence of the reference area ( 5 c ) at one detection area ( 7 c ), and to generate at least one corresponding output electrical signal (s 7 ), in response to detection of the reference area ( 5 c ); at least one elaboration and program control unit ( 8 ) receives as an input at least one of the output electrical signals (s 7 ) and generates at least one electrical signal (s 8 ) of detection; activation of the detector ( 7 ) (phase 100 ); elaboration by at least one of the elaboration and program control units ( 8 ) of at least one of the signals (s 7 ) which are from the detector ( 7 ) (phase 200 ), the elaboration phase including a comparison (phase 220 ) between at least one of the output electrical signals (s 7 ) and the respective maximum and minimum reference thresholds (S max , S min ); based on the elaboration (phase 200 ), generating electrical signal of detection (s 8 ) by at least one of the elaboration and program control units ( 8 ) (phase 300 ); the maximum and minimum reference thresholds (S max , S min ) being periodically updated.

What is claimed is: 
     
       1. A method of detecting the reciprocal position between a cylinder and a piston in a cylinder-piston unit, said method comprising the steps of:
 arranging a cylinder-piston unit including:
 at least one tubular body having at least one through receiving seat; 
 at least one moving body longitudinally translatable in said tubular body, said moving body being provided with at least one reference area extending for a portion on the surface of said moving body, along the longitudinal axis of said moving body; 
 at least detecting means, receivable in said through receiving seat of said tubular body, faced towards said moving body in said tubular body, and designed to detect the presence or absence of said reference area at a detection area thereof, and to generate at least one corresponding output electrical signal, in response to the detection or not of said reference area of said moving body; 
 at least one program control and processing unit, designed to receive in input said at least one output electrical signals from said detecting means and to generate in output at least one electrical signal of detection; 
 
 activating said detecting means; 
 processing, by said at least one program control and processing unit, said at least one signals output from said detecting means, said processing step including a comparison between said at least one output electrical signal and respective maximum and minimum reference threshold values (S max , S min ); 
 generating, based on said processing an electrical signal of detection by said at least one program control and processing unit; 
 wherein said maximum and minimum reference threshold values (S max , S min ) are calculated based on average values of the amplitudes of a plurality of sample of said one output electrical signal and periodically updateable according to the following relationships:
     S   min =[(average in reference area+average in absence reference area)−hysteresis]/2
 
     S   max =[(average in reference area+average in absence reference area)+hysteresis]/2 
 
 
       wherein said “hysteresis” is a predetermined value, said “average in reference area” corresponds to the average value of the amplitudes of said plurality of samples of said signal detected at said reference area, and said “average in absence reference area” corresponds to the average value of the amplitudes of said plurality of samples of said signal detected at an area outside said reference area. 
     
     
       2. A method according to  claim 1 , characterized in that it includes a periodic comparison (step  2211 ) between the values of said maximum and minimum reference threshold values (S max , S min ) and first maximum and minimum threshold values (PS max , PS min ). 
     
     
       3. A method according to  claim 2 , wherein if said comparison shows a difference between the values of said maximum and minimum reference threshold values (S max , S min ) and said first maximum and minimum threshold values (PS max , PS min ), higher than a predetermined threshold value, then the values of said first maximum and minimum threshold values (PS max , PS min ) are set equal to the threshold values of said maximum and minimum reference threshold values (S max , S min ). 
     
     
       4. A method according to  claim 2 , wherein said periodic comparison between said values of said maximum and minimum reference threshold values (S max , S min ) and said first maximum and minimum threshold values (PS max , PS min ) is executed less frequently than the update of said maximum and minimum reference threshold values (S max , S min ). 
     
     
       5. A method according to  claim 1 , further comprising a calibration step of said detecting means. 
     
     
       6. A method according to  claim 5 , wherein said calibration step comprises:
 the positioning, at said detection area of said detecting means, of a material used in said reference area; 
 the activation of said detecting means; 
 the adjustment of said electrical signal output from said detecting means; 
 the positioning, at said detection area of said detecting means, of a material used in said moving body outside said reference area; 
 the activation of said detecting means; 
 the adjustment of said electrical output signal output from said detecting means. 
 
     
     
       7. A method according to  claim 6 , wherein said steps of adjustment of said electrical signal output from said detecting means comprise the use of a digital trimmer. 
     
     
       8. A cylinder-piston unit for implementing the method of detection of the reciprocal position between a cylinder and a piston according to  claim 1 , comprising:
 at least one tubular body provided with at least one through receiving seat; 
 at least one moving body longitudinally translatable in said tubular body, said moving body being provided with at least one reference area extending for a portion on the surface of said moving body, along the longitudinal axis of said moving body; 
 at least detecting means receivable in said through receiving seat of said tubular body, faced towards said moving body in said tubular body, and designed to detect the presence or absence of said reference area at a detection area thereof, and to generate at least one corresponding output electrical signal, in response to the detection or not of said reference area of said moving body; 
 at least one program control and processing unit, designed to receive in input said at least one output electrical signal from said detecting means, and generate in output at least one electrical signal of detection; 
 
       wherein said program control and processing unit comprises at least one pre-processing step of said at least one output electrical signal and in that said detecting means are removably receivable in said receiving seat according to at least one operative configuration, so that, depending on said at least one operative configuration, the output electrical signal from said pre-processing stage of said program control and processing unit has, at the portion thereof of detection of said reference area, a width which is substantially equal or narrower or wider than the dimension of said portion of said reference area along the longitudinal axis of said moving body. 
     
     
       9. A cylinder-piston unit according to  claim 8 , wherein said at least one operative configuration of said detecting means comprises at least one emitting means of light radiation and at least one receiving means for said light radiation located along an axis parallel to the longitudinal axis of said cylinder-piston unit. 
     
     
       10. A cylinder-piston unit according  claim 8 , wherein said operative configuration of said detecting means comprises at least one emitting means of light radiation and at least one receiving means for said light radiation, located along an axis orthogonal to the longitudinal axis of said cylinder-piston unit. 
     
     
       11. A cylinder-piston unit according to  claim 8 , wherein said operative configuration of said detecting means comprises two emitting means and two receiving means located side by side, said receiving means being placed at the opposite ends of said operative configuration. 
     
     
       12. A cylinder-piston unit according to  claim 8 , wherein said operative configuration of said detecting means comprises one emitting means and two receiving means located side by side, said receiving means being placed opposite with respect to said emitting means. 
     
     
       13. A cylinder-piston unit according to  claim 8 , wherein said receiving means of said operative configuration of said detecting means are placed spaced from the other. 
     
     
       14. A cylinder-piston unit according to  claim 8 , wherein said pre-processing stage of said at least one output signal is designed to implement at least one logic function selected among an AND, or an OR or a SUM or a PRODUCT or a DIFFERENCE or a DIVISION function or a combination thereof. 
     
     
       15. A cylinder-piston unit according to  claim 14 , wherein said pre-processing stage designed to implement at least one logic function provides for the implementation of said logic function the use of at least one corresponding logic gate selected among an AND or an OR or a SUM or a PRODUCT or a DIFFERENCE or a DIVISION function or a combination thereof. 
     
     
       16. A method of modifying the width of the electrical signal of detection output from a program control and processing unit of a cylinder-piston unit according to  claim 8 , at the portion thereof of detection of said reference area, said cylinder-piston unit comprising said detecting means received in said through receiving seat according to an operative configuration, said method including the step of moving said detecting means in said receiving seat from said operative configuration to said at least another operative configuration. 
     
     
       17. A method according to  claim 16 , wherein said step of moving said detecting means in said receiving seat from said operative configuration to said at least another operative configuration comprises a step of rotating of about 90° said detecting means.